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The role of hafnium in modifying the microstructure of cast nickel-base superalloys

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Abstract

The effects of hafnium additions on the microstructure of ALLOY 713-LC have been investigated using electron microscopy and by a radiographic technique which reveals the grain boundary structure. It is shown that the Chinese script MC carbides in ALLOY 713-LC are altered to a particulate morphology in alloy MM-004 (hafnium-modified ALLOY 713-LC). Unlike the script carbides, the discrete MC particles do not provide any easy path for rapid crack propagation and hence, ductility is enhanced. In the hafnium-bearing alloy, the morphology of γ’ phase is also modified. Colonies of ((γ + γ′) with a rosette morphology are formed and individual γ’ platelets exhibit dendritic growth. It is shown that this morphology of γ’ causes grain boundaries to be distorted from planar equilibrium interfaces to a convoluted interlocking configuration. It is suggested that the interlocking boundaries retard grain boundary sliding and separation during creep and result in higher stress-rupture life for hafnium-modified alloys.

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Authors and Affiliations

  1. Union Carbide Research Institute, Tarrytown, N.Y.

    P. S. Kotval (Senior Staff Scientist)

  2. Research Institute for Advanced Studies, USA

    J. D. Venables (Senior Research Scientist) & R. W. Calder

Authors
  1. P. S. Kotval
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  2. J. D. Venables
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  3. R. W. Calder
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Formerly with Research Institute for Advanced Studies, Baltimore, Md.

Formerly with Research Institute for Advanced Studies.

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Kotval, P.S., Venables, J.D. & Calder, R.W. The role of hafnium in modifying the microstructure of cast nickel-base superalloys. Metall Trans 3, 457–462 (1972). https://doi.org/10.1007/BF02642049

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  • DOI: https://doi.org/10.1007/BF02642049

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